Synonyms for Eternity:

n.

hades, afterlife, infernal, the (great) beyond, the next life, the hereafter. consistency, survival, eternalness, continuity, Sempiternity, stability, eternality, longevity, preservation, limited, continuation. continue. live, deathlessness, everlasting life. blue moon, long, year. eternity (noun)
timelessness, timeless existence, forever, infinity.
forever (noun)
afterlife, ages, endlessness, perpetuity, blue moon, infinity, age, everlastingness, timelessness, aeon, world without end, immortality.
heaven (noun)
bliss, azure, happiness, eden, immortality, shangri-la, land o'goshen, pinnacle, spire, afterworld, culmination, stratosphere, mountaintop, fairyland, ether, everlastingness, summit, canaan, zion, hereafter, dreamland, heaven, joyfulness, zenith, goshen, glory, acme, nirvana, wonderland, apex, rhapsody, ecstasy, paradise, climax.
indefinite duration (noun)
age, era, lapse, forever, time, span, duration, aeon.
infinity (noun)
ceaselessness, Innumerability, limitlessness, Incalculability, infinity, Immeasurability, endlessness, perpetuity, Inexhaustibility, boundlessness, interminability, timelessness.
long time (noun)
time immemorial.
perpetuity (noun)
continuousness, constancy, endurance, permanence, time immemorial, lastingness.
time (noun)
infinity.

Other synonyms:

blue moon, everlasting life, infernal, eternalness, hades, deathlessness, consistency, longevity, eternality, afterlife, the hereafter, survival. stability, epic, continuity, eon. year, continuation. preservation. long. Other relevant words:
stability, eon, timeless existence, survival, everlasting life, blue moon, afterlife, consistency, continuity, year, eternalness, long, preservation, eternality, deathlessness, ages.

Usage examples for eternity

  1. That would have been to give eternity to my misery. – The Flight of the Shadow by George MacDonald
  2. Think of this also, that for aught we know, such an object lesson may be needed to all eternity as a warning against sin. – Love's Final Victory by Horatio
  3. Surely mistakes can't last through eternity – Kildares of Storm by Eleanor Mercein Kelly